Research On Vertical Handoff Algorithm In Heterogeneous Wireless Networks

The goal which is achieved on communications technology is that whoever can communicate with another person in any way in whenever or wherever in the future. With the innovation of technology, there were a variety of issues in networks, which included coverage and bandwidth is limited. The need of future communication cannot be satisfied by a single network, but it could be satisfied by various networks. Therefore, it was very valuable that the vertical handover algorithms were researched in heterogeneous networks.Vertical handover algorithms could depend on the signal intensity values of various networks primarily to study in existing heterogeneous networks. This paper would summarize existing vertical handover algorithms in heterogeneous networks. For a series of conditions which might include interference problems in heterogeneous networks, the features of wireless local area network(WLAN), in order to get the best user experience and communication, always access the best network, and then based on the needs of different communication services in real-life, two different vertical handover algorithms were proposed on different emphases in heterogeneous network, as follows:First and foremost, in order to achieve seamless connectivity in heterogeneous networks, it was important to enhance the location awareness of the mobile station(MS) as well as to reduce the adverse effect of fading. It was able to predict future network conditions accurately. A Savitzky-Golay filtering based vertical handoff algorithm was adopted in this paper, which could equip the MS to decide network coverage boundaries accurately. Simulation results showed that this method could reduce the effects of fading in the received signal. Meanwhile, it could also reduce the ping-pong effect effectively and improve the performance of the network.Secondly, there were several factors which might affect the choice of a variety of networks in heterogeneous wireless networks. In view of this problem and another question that different traffics had different quality of service(QOS), an AHP-GRA-based vertical handover algorithm was proposed. The Analytic Hierarchy Process(AHP) could be utilized to calculate the weights of judgment factors in the various networks, which combined with Gray Relational Analysis(GRA) to determine the Gray weighted correlation values of candidate networks. The size of the gray-weighted correlation values would be compared to access the best network. Simulation results showed that the algorithm could solve the problem of load balancing among networks effectively, and its advantages could include the characteristic with straightforward calculation, easy implementing and great flexibility.